“Blood, saliva, epithelial cells,” Aaron says. “Start with Lydia Webster’s toothbrush and blood from the bathroom floor. We have a good idea about her DNA, mainly important so we can exclude her. Or identify her eventually.” As if there’s no doubt she’s dead. “Then there’s a different profile from the skin cells, the sand and glue recovered from the broken window in her laundry room. And the burglar-alarm keypad. The dirty T-shirt from the laundry basket. All three have her DNA, unsurprisingly. But also a profile from someone else.”

“What about Madelisa Dooley’s shorts?” Scarpetta asks. “The blood on them.”

Aaron says, “Same donor as the three I just mentioned.”

“The killer, we think,” Lucy says. “Or whoever broke into her house.”

“I think we should be careful saying that,” Scarpetta says. “There have been other people in her house, including her husband.”

“The DNA’s not his, and we’ll tell you why in a minute,” Lucy says.

Aaron says, “What we did was your idea—going beyond the usual profile matching in CODIS and opening up the search by using the DNAPrint technology platform you and Lucy have discussed—an analysis that uses paternity and sibship indices to arrive at a probability of relatedness.”

“First question,” Lucy says. “Why would her ex-husband leave blood on Madelisa Dooley’s shorts?”

“Okay,” Scarpetta agrees. “That’s a good point. And if the blood is the Sandman’s—and to be clear, I’m going to call him that—then he must have injured himself somehow.”

“We might know how,” Lucy says. “And we’re beginning to have an idea of who.”

Aaron picks up a file folder. He takes out a report and hands it to Scarpetta.

“The unidentified little boy and the Sandman,” Aaron says. “Knowing that each parent donates approximately half of his or her genetic material to their child, we can have an expectation that samples from a parent and a child are going to indicate their relationship. And in the case of the Sandman and the unidentified little boy, a very close family relationship is implicated.”

Scarpetta looks at the test results. “I’ll say the same thing I did when we got the fingerprint match,” she says. “Are we sure there’s no mistake? No contamination, for example?”

“We don’t make mistakes. Not like that,” Lucy says. “You get only one and you’re done.”

“The boy is the Sandman’s son?” Scarpetta wants to make sure.

“I’d like references and investigation, but I certainly suspect it,” Aaron replies. “At the very least, as I said, they’re closely related.”

“You mentioned his being injured,” Lucy says. “The Sandman’s blood on the shorts? It’s also on the broken crown you found in Lydia Webster’s bathtub.”

“Maybe she bit him,” Scarpetta says.

“A very good chance,” Lucy says.